There is a demand for new motor drive systems for converting between electrical and mechanical energy, which have both high operating efficiency and minimized construction costs. One method for creating increased efficiency motors is to utilize a construction having permanent magnet excitation, along with an air core armature. Air core armatures contain their windings in the magnetic air gap of the motor instead of within slots in a laminated steel stator. Permanent magnets drive the flux across the air gap. This construction affords a reduction in eddy current and hysteresis losses in the stator, but it also entails an increased magnetic air gap. Unlike induction or asynchronous type motors, permanent magnet motors are synchronous and typically cannot line start. They must therefore be driven by a variable speed motor drive inverter that ramps up the speed from stopped. Because of the combined operation of motor and electronic drive, each component cannot be satisfactorily designed for maximum performance alone. A new drive system for motor and variable speed drive combination having increased efficiency, while also minimizing costs, is needed.